Sedimentary Facies Research Of Chang 6 In Yanwu Area, Ordos Basin

The research area of this paper is located in the southwest of Ordos Basin.As the main reservoir of Changqing Oilfield,the Yanchang Formation is of great significance for exploration and development.After large-scale development in recent years,the Triassic Chang 6 reservoir in Yanwu area is mainly concentrated in the eastern region,with a high degree of development and insufficient potential of available resources.In recent years,with the continuous exploration work,Yan 135,Zhen191 and other wells in the western Yanwu oilfield have been found to have a certain scale of oil reservoirs.At the same time,industrial oil flow has also been obtained at the well sites of Zhen292,Yan180 and Meng 20 in the Triassic Chang 6 formation.Therefore,Chang 6 reservoir in the western Yanwu oilfield is the key reservoir for the resource replacement of the eleventh oil production plant in Changqing oilfield.Through geological research of Chang 6 formation in Yanwu area.It can provide theoretical basis and technical support for future oil and gas exploration and development.This paper mainly focuses on the sedimentation of the Chang 6 Formation of Triassic in Yanwu area.The methods of stratigraphic division and correlation,provenance study,sedimentary facies division,single well column diagram and connecting well diagram analysis are used.The final understanding is as follows:?1?The strata of Chang 6 reservoir group in Yanwu area are divided and correlated in detail.Based on the methods of marker beds,sedimentary cycles,lithologic thickness correlation and sequence stratigraphy theory,the fine stratigraphic division and correlation work has been carried out,and the stratigraphic correlation markers in this area have been found.Firstly,Chang 6 strata are subdivided into three sublayers:Chang6₁,Chang 6₂ and Chang 6₃.Then,the three sublayers are divided into Chang 6₁¹,Chang6₁²,Chang 6₂¹,Chang 6₃¹ and Chang 6₃²,totaling 6.Twelve skeleton profiles,including six cross-sectional and vertical skeleton profiles,are established in the work area.?2?It is clear that the sedimentary system of the Chang 6 Member belongs to braided river delta sediments controlled by Southwest provenance.The sedimentary subfacies are braided river delta plain and Braided River Delta front.Semi-deep lake sediments and gravity flow sediments also occur in the northeastern part of the study area.?3?The sedimentary facies characteristics of Chang 6 reservoir in Yanwu area are studied by using the idea of point-to-line and surface-to-surface sedimentary research.The sedimentary facies model of Chang 6 reservoir in Yanwu area is established through well location analysis from single well facies to connecting well facies,combined with sedimentary microfacies plane distribution map and sand body plane distribution map.?4?The distribution characteristics of sand bodies in the study area are approximately the same as that of sedimentary microfacies.The distribution direction of sand bodies is from southwest to northeast,with wide strip or sheet distribution.The connectivity of sand bodies is better from southwest to northeast along source direction,but the connectivity of sand bodies from northwest to southeast along vertical source direction is worse than that along source direction.In summary,the strata of Chang 6 member of Yanchang Formation in the work area are divided and compared in detail at first.On this basis,the sedimentary environment and sedimentary characteristics of different horizons and sections are analyzed,the structural characteristics of Chang 6 marker layer are studied,the sedimentary microfacies research is carried out,and the sandbody distribution laws of different horizons in the study area are depicted.It has contributed to the study of sedimentary facies of the Chang 6 member of the Triassic Yanchang Formation in Yanwu area.